Hi Sarang37,

To start, when posting GMAT questions, it's important to post the entire prompt (including the 5 answer choices). Sometimes the answers are written in a way that provides a clue as to how you might approach the prompt (and possibly a way to avoid a 'math heavy' approach). GMAT questions sometimes provide information 'out of order', so you might have to reorganize the given information before you can properly work through it.

Here, we're asked to compare 90 to some other number. That number is 5 times greater than 30% of 40.

30% of 40 = (.3)(40) = 12
5 times 12 = 60

90 is what percent greater than 60? Here, we'll need the Percent Change Formula:

(New - Old)/(Old) = (90 - 60)/(60) = 30/60 = 1/2 = 50% greater

GMAT assassins aren't born, they're made,
Rich